Single-crystalline β-Ga 2O 3 epilayer on (0001) sapphire was grown at low temperature and low pressure by MOCVD. The as-grown β-Ga 2O 3 epilayer was annealed at 800°C in atmosphere. Crystal structure and quality of the epilayer remained the same after annealing. Influence of surface states and point defects of β-Ga 2O 3 epilayers before and after annealing are studied using room-temperature Photoluminescence (PL) and I-V characteristics. The significant difference in PL property of β-Ga 2O 3 and big difference (∼5 orders in magnitude) in dark current before and after annealing is attributed to the healing of the surface states and point defects. Gallium oxide is known for its high density of oxygen vacancies. Annealing single-crystalline β-Ga 2O 3 epilayer at high temperature makes the healing possible, probably due to oxygen adsorption. A significant healing of surface states and point defects in single-crystalline β-Ga 2O 3 indicates its high potential in fabrication of optoelectronic devices.